This invention relates in general to earth boring bits and in particular to an insert with improved means for preventing rotation in its receptacle.
Earth boring tool bits include those which have tungsten carbide inserts interferingly retained in mating holes or receptacles in a supporting structure of the bit. The cutting tip or protruding end of the insert serves to crush and disintegrate the earth formation. The supporting structure for the inserts is normally a head or conical cutter of steel. Holes are drilled and reamed in the exterior surface of the supporting structure. The inserts are then pressed into the holes with an interference fit.
While successful, the large forces imposed on the inserts tend to cause the inserts to rotate in their holes. In the case of a specially shaped insert, such as a chisel-shaped insert, the insert will become less effective if it is turned from its proper orientation.
The tight interference fit is the main means by which the inserts are kept from rotating. In U.S. Pat. No. 3,581,835, issued to Frank E. Stebley, Mar. 28, 1972, grooves or flutes are formed on the sidewall of the insert to prevent rotation. Another proposal, shown in U.S. Pat. No. 4,199,035, issued to Donald A. Thompson, on Apr. 22, 1980, teaches the use of a dowel or locating pin for locking the insert to the supporting structure.